In electrical installations with switchable load feeders, there is often the need to switch the switching members, such as contactors, in dependence on one another. These sometimes complex circuits often require logic operations, interrogation of the switching states, driving of the switching devices and interlocks and are therefore often associated with a great deal of wiring complexity in the control current circuit. In addition, additional devices such as timing relays or auxiliary switches, are required which often need to be wired to each individual switching device.
Complex circuits are therefore constructed by wiring of the control current circuits in which the switching devices are also wired to the additional components, such as timing relays and auxiliary switches, which can drive up the total costs of the installation and complicate the design of the complex circuits. Depending on the fitter, the switching devices, in particular contactors, are wired differently. As a result of the replacement of switching devices, in particular with ones from different manufacturers, it is often no longer possible for others to understand the wiring, with the result that increased complexity is involved in getting a look at the wiring of the individual switching devices and the additional devices in this case.